1. Field of the Invention
The present invention relates to a braking-force generator which generates braking force corresponding to an electric signal generated on the basis of an operational input by an operator.
2. Description of the Related Art
The braking-force generator does not need direct exertion of the force produced by the driver as braking force for a vehicle, and can realize the so-called brake-by-wire (BBW) system. (See, for example, Japanese Registered Patent No. 4801823.)
In the past, generally, when an abnormality occurs in a device such as the braking-force generator, it was difficult for the device to solve the abnormality by itself. However, currently, as in the typical case where the artificial intelligence is used, the device can solve by itself an abnormality occurring in the device, so that the device can be restored to the normal state. The braking-force generator diagnoses by itself the braking-force generator for abnormality. When the braking-force generator makes a diagnosis of an abnormality, the braking-force generator takes a measure for solving the abnormality, so that the braking-force generator can be restored to the normal state. When the braking-force generator diagnoses by itself the braking-force generator for abnormality again after taking the above measure, and determines that the abnormality is solved and the braking-force generator is in the normal state (i.e., the abnormality is solved), it is possible to determine whether or not the braking-force generator is restored to the normal state. A conceivable example of an abnormality in the braking-force generator which can be automatically restored is a dislocation of a piston (and a push rod for pushing the piston and a motor for sliding the push rod). In order to generate the braking force with high precision, it is desirable that the dislocation be minimized. In this case, it is possible to determine that an abnormality occurs when the dislocation is equal to or greater than a predetermined value. That is, the capability of automatically solving an abnormality and automatically keeping the dislocation below a predetermined value is considered to be useful for generating the braking force with high precision.
The braking-force generator generates the braking force by a servo mechanism. The servo mechanism makes the generated braking force follow target values which are successively set. However, when an abnormality occurs in the braking-force generator, the servo mechanism needs to be temporarily prohibited (stopped) in order to perform operations for automatically recovering from the abnormality. After the abnormality is solved, the operation of the servo mechanism is restarted. At the time at which the operation of the servo mechanism is restarted, the driver may or may not be pushing the brake pedal. If the operation of the servo mechanism is restarted when the driver is not pushing the brake pedal, the braking force increases regardless of the intention of the driver, so that the driver will feel a sense of incongruity.
In view of above, the object of the present invention is to provide a braking-force generator which does not cause the driver to feel a sense of incongruity even when the braking-force generator performs an operation for automatically recovering from an abnormality.